1. Field of the Invention
The present invention relates to a focusing control device, a focusing control method, a non-transitory computer readable recording medium storing a focusing control program, a lens device, and an imaging device.
2. Description of the Related Art
In recent years, with an increase in resolution of imaging elements, such as a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor, there is a rapid increase in demand for information devices having an imaging function, such as a digital still camera, a digital video camera, and a mobile phone, such as a smartphone. The information devices having an imaging function described above are referred to as imaging devices.
In these imaging devices, as a focusing control method which focuses on a main subject, a contrast auto focus (AF) method or a phase difference AF method (for example, see JP2010-008507A, JP2011-059384A, and JP2001-004910A) is employed. Since the phase difference AF method can perform high-speed processing, the phase difference AF method is a method effective for moving image capturing where a subject is continuously imaged with an imaging element.
JP2010-008507A describes an imaging device which predicts a current focus lens position based on defocus amounts calculated by a phase difference detection method multiple times in the past.
JP2011-059384A describes an imaging device which calculates the amount of change of an image plane position using a prediction function based on the image plane position determined by a defocus amount detected during imaging and a position of an imaging lens, and a release time lag as a predetermined time, and calculates a target position of the image plane position.
JP2001-004910A describes an imaging device which detects a moving speed of a subject based on defocus amounts calculated by a phase difference detection method multiple times in the past.